As a mage enthusiast for the better part of 2 decades I am probably the most highest qualified person to report this in the history of ultima. The difference is very small / not noticeable for players on higher ping or that dont use mages specifically for pvp. It hit me like a punch in the face. I started running some tests OSI vs Heritage. Here are my findings.
I believe the problem is that uoguide is often updated carelessly or not updated at all. [The player who made it does not play the game anymore for medical reasons.]

Using this example [As it has no target and therefor no human error]
.5s is wrong. It is a 1s spell that only gets to .5s AFTER you add fc2.
To prove that I went to test center and timed a 0fc cast [1s] vs a fc2 cast [.5s]. Then I added recovery and tapped the macro 10 times consecutively to which OSI produced 2 [food]. On heritage the same test yielded 5[food].
My guess is that every spell on heritage that used uoguide as a base could be off.
Happy to conduct more testing, Im going to test the other spell schools when I finally make chars that use them on heritage. Keep up the good work boys!
I believe the problem is that uoguide is often updated carelessly or not updated at all. [The player who made it does not play the game anymore for medical reasons.]

Using this example [As it has no target and therefor no human error]
.5s is wrong. It is a 1s spell that only gets to .5s AFTER you add fc2.
To prove that I went to test center and timed a 0fc cast [1s] vs a fc2 cast [.5s]. Then I added recovery and tapped the macro 10 times consecutively to which OSI produced 2 [food]. On heritage the same test yielded 5[food].
My guess is that every spell on heritage that used uoguide as a base could be off.
Happy to conduct more testing, Im going to test the other spell schools when I finally make chars that use them on heritage. Keep up the good work boys!